Greenbrier Cos. (GBX) rejected a sweetened bid from American Railcar Industries (ARII) , which is controlled by investor Carl Icahn. Greenbrier shares tumbled 11.1% and American Railcar shares were down 2.6%.

The board of flash-memory maker SanDisk(SNDK) approved an additional $750 million for stock buybacks, bringing the total stock repurchase authorization to $1.25 billion. Shares added 0.20%.

Ameristar Casinos (ASCA) announced that it has agreed to be acquired by Pinnacle Entertainment (PNK) for $26.50 a share in cash, representing a premium of 45% over the average closing price of Ameristar common stock for the 90 days ended Dec. 20. Ameristar shares soared 20.1%, while Pinnacle Entertainment shares jumped 21.4%.

AbbVie( ABBV ) , which is being spun off by Abbott Laboratories (ABT) , is set to replace Dell(DELL) in the S&P 100 and Federated Investors (FII) in the S&P 500. Dell shares lost 0.67% and Federated shares gave up 2.1%.